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A009818
Expansion of e.g.f.: tanh(tan(x)/cos(x)).
0
1, 3, -23, -2149, -73967, 4773747, 1496400505, 166245767819, -17997337551071, -15656779903415325, -4002361029690394103, 437839261718446458491, 1025307746504958768359473, 499247007876089430591206739
OFFSET
0,2
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[Tanh[Tan[x]/Cos[x]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, May 21 2021 *)
CROSSREFS
Sequence in context: A088056 A009593 A351107 * A210734 A166315 A371346
KEYWORD
sign
AUTHOR
EXTENSIONS
Extended with signs by Olivier Gérard, Mar 15 1997
Definition clarified and prior Mathematica program replaced by Harvey P. Dale, May 21 2021
STATUS
approved